It was noted that theoretical studies had shown that the neutral Si vacancy, VSi, in cubic 3C-type material exhibited a negligible Jahn-Teller distortion, and that this provided an opportunity to study the energy sequence of various multiplets in a vacancy with genuine Td symmetry. Calculations which were performed using the local spin density approximation gave a spin triplet as the ground state. However, determination of the true ground state required the incorporation of configuration interactions. By using multi-configurational self-consistent field calculations, it was shown that the ground state of the neutral VSi0 in 3C-type material was a spin singlet. It was concluded that the calculated energy difference, 0.1eV, in favor of the singlet spin state would still permit experimental observation of the triplet state at high temperatures.

The Spin State of the Neutral Silicon Vacancy in 3C-SiC. P.Deák, J.Miró, A.Gali, L.Udvardi, H.Overhof: Applied Physics Letters, 1999, 75[14], 2103-5